The present invention relates to a joint prosthesis and method of producing same.
Within this application several publications are referenced by arabic numerals within parenthesis. Full citations for these references may be found at the end of the specification immediately preceding the claims. The disclosures of all of these publications in their entireties are hereby incorporated by reference into this application in order to more fully describe the state of the art to which this invention pertains.
Various joint prostheses have been designed and produced, such as the Swanson trapezial implant, the Swanson condylar implant, the De la Caffiniere prosthesis, the Braun design, the Kessler design, the Mayo clinic prosthesis, the Helal spacer, the Eaton trapezial implant, and the Niebauer xe2x80x9ctie-inxe2x80x9d design.
In addition, various patents have been granted on joint prostheses and methods of making them. For example, U.S. Pat. No. 4,704,686 to Aldinger (xe2x80x9cAldingerxe2x80x9d) relates to the fabrication of bone replacement prosthesis using tomography. Specifically, tomographic pictures of cross-sections of the bone are taken to determine characteristics of the bone, such as the locations of different bone densities. This data is then used to calculate the size and placement of a series of disks which when connected form the desired prosthesis shape. The prosthesis is machined according to these calculations. The use of bone cement is minimized or eliminated because the accurate shape of the resulting prosthesis leaves little space between the prosthesis and the remaining bone.
Although Aldinger discusses the custom fabrication of prostheses based on the shape and density of the patient""s bone so that a prosthesis can be press-fit into the bone, the patent does not teach the use of imaging data to custom fabricate anatomic articular surfaces for the joint itself. In this regard it is noted that as used herein the terms xe2x80x9canatomicxe2x80x9d and xe2x80x9canatomically accuratexe2x80x9d may relate to shapes that are either calculated or stored in a database. Moreover, it is noted that the term xe2x80x9cspline surfacesxe2x80x9d is a general term that includes both biquintic and B-spline surfaces, for example.
In U.S. Pat. No. 5,037,440 to Koenig (xe2x80x9cKoenigxe2x80x9d), each anchor stem of a prosthesis is press-fit into a hole created in the bone on a respective side of the joint. One anchor has a complex convex surface which wraps around the end of the bone and the other anchor has a complex concave surface. The only contact between the anchors, which are not attached, are the complex surfaces which can slide against each other. The surfaces are not, however, anatomically correct.
U.S. Pat. No. 4,725,280 to Laure (xe2x80x9cLaure ""280xe2x80x9d) shows a saddle-like finger joint prosthesis having a xe2x80x9cVxe2x80x9d-shaped tab anchor and a valley-shaped slot anchor. Specifically, the xe2x80x9cVxe2x80x9d-shaped tab anchor has concave sides and the slot anchor has convex sides. Since the tab anchor slides along the bottom of the valley of the slot anchor, undesired sideward movement of the joint is restricted. While the two anchors are not attached to each other, the prosthesis does not provide for two anatomically correct contact and load-bearing surfaces.
U.S. Pat. No. 4,276,660 to Laure (xe2x80x9cLaure ""660xe2x80x9d) relates to a thumb joint prosthesis that utilizes a ball and socket configuration. Again, this patent does not teach anatomically correct contact and load-bearing surfaces.
U.S. Pat. No. 5,150,304 to Berchem et al. (xe2x80x9cBerchem et al.xe2x80x9d) relates to a method of fabricating an implantable joint prosthesis. Specifically, a computer determines the shape of the joint prosthesis before surgery from computations, such as finite element analysis, so that undercuts can be eliminated and so that the stress is uniformly distributed. The computations are based on data received from imaging scans of the patient""s bone. Once the shape of the bone is determined the prosthesis is either selected from a collection of prostheses or machined using computer-aided manufacturing.
While the Berchem et al. patent discusses the use of a mathematical model for making a joint implant prosthesis based on imaging results of the patient""s bone, there is no teaching to use mathematically described anatomic joint surfaces derived from the examination of other joints to create the prosthesis. Furthermore, unlike the anatomically correct joint surfaces of the subject invention, the non-articular surface is tailored to reduce stress and not to recreate a healthy articular joint surface.
U.S. Pat. No. 4,436,684 to White (xe2x80x9cWhitexe2x80x9d) relates to a method of forming implantable prosthesis for reconstructive surgery. A selected internal skeletal structure is measured by subjecting the body to radiant energy to produce radiant energy responses that are detected to obtain representations delineating the skeletal structure. Three dimensional coordinate data defining the skeletal structure is generated from the obtained representations. The coordinate data is employed to control a sculpting tool to form the prosthesis.
While the White patent discusses the use of radiant energy to obtain skeletal structure information utilized to fabricate a prosthesis, there is no teaching to use mathematically described anatomic joint surfaces, or archetypes, derived from the examination of other joints to create the prosthesis.
Accordingly, it is an object of the present invention to provide a joint prosthesis in which the relative motion of the two components of the joint is provided by sliding motion between two anatomically accurate surfaces.
It is a further object of the present invention to provide a joint prosthesis in which the motion of the joint is physiologic because the contacting articular surfaces are anatomic in shape and highly accurate in topography.
It is a further object of the present invention to provide a joint prosthesis in which constraints that result from the articular surface shapes at their extremes of motion contribute to reducing stress in capsular tissues, as occurs in physiologic conditions.
It is a further object of the present invention to provide a joint prosthesis in which loosening of the prosthesis can not result from distraction of the joint because the articular contacting surfaces are not attached.
It is a further object of the present invention to provide a joint prosthesis in which load transmission across the joint mimics physiologic conditions due to the highly accurate shape of the articular contacting surfaces.
It is a further object of the present invention to provide a joint prosthesis in which the geometry of the contact surfaces is described using spline surfaces which will reproduce highly accurately the shape of physiologic contact surfaces.
It is a further object of the present invention to provide a joint prosthesis in which both components of the joint prosthesis are press fit into respective bones of the joint.
It is a further object of the present invention to provide a joint prosthesis in which the surfaces of the joint prosthesis which come into contact with bone may be shaped and/or coated to promote an intimate bone/prosthesis interface bond and to promote functional stress transfer.
According to one aspect of the present invention, a joint prosthesis for attachment to a bone of a patient is provided, comprising an anchor with a head surface and a stem for attachment to an end of the bone, the head surface having an anatomically accurate shape.
According to another aspect of the present invention, a total joint prosthesis for attachment to two bones of a patient is provided, comprising two unjoined anchors, each with a head surface and a stem for attachment to ends of respective ones of the two bones, each of the head surfaces having an anatomically accurate shape.
According to another aspect of the present invention, a total joint prosthesis for attachment in the bones of a patient is provided, comprising two unjoined anchors, each with a head surface and a stem for attachment to end of respective ones of the two bones, each of the head surfaces having an anatomically accurate shape based upon a particular one of a plurality of articular joint surfaces within a database of mathematical descriptions of said plurality of articular joint surfaces.
According to another aspect of the present invention a method of manufacturing a joint prosthesis for a patient with a healthy contralateral joint is provided, comprising obtaining imaging data of the patient""s healthy contralateral joint surfaces, comparing the imaged data of the patient""s healthy contralateral joint surfaces with a database of mathematical descriptions of a plurality of articular joint surface archetypes to determine which one of the plurality of articular joint surface archetypes exhibits the smallest deviation in overall dimensions from the imaged data, and fabricating the joint prosthesis to resemble the articular joint surface archetype which exhibits the smallest deviation in overall dimensions from the imaged data.
According to another aspect of the present invention a method of selecting, from a collection, a joint prosthesis for a patient with a healthy contralateral joint is provided, comprising obtaining imaging data of the patient""s healthy contralateral joint surfaces, comparing the imaged data of the patient""s healthy contralateral joint surfaces with a database of mathematical descriptions of a plurality of articular joint surface archetypes to determine which one of the plurality of articular joint surface archetypes exhibits the smallest deviation in overall dimensions from the imaged data, and selecting, from the collection, the joint prosthesis which exhibits the smallest deviation in overall dimensions from the articular joint surface archetype which exhibits the smallest deviation in overall dimensions from the imaged data.
According to another aspect of the present invention a method of manufacturing a joint prosthesis for a patient with a healthy contralateral joint is provided, comprising obtaining imaging data of the patient""s healthy contralateral joint surfaces, fabricating a mirror image replicate of the patient""s imaged healthy contralateral joint surfaces.
According to another aspect of the present invention a method of manufacturing a joint prosthesis for a patient""s bone is provided, comprising measuring a plurality of parameters including dimensions of the bone, the patient""s weight, the patient""s sex, and the patient""s height, comparing the plurality of measured parameters with a respective plurality of corresponding parameters in a database of mathematical descriptions of a plurality of articular joint surface archetypes to determine which one of the plurality of articular joint surface archetypes has parameters exhibiting the most similarity to the measured parameters, and fabricating the joint prosthesis to resemble the articular joint surface archetype which has parameters exhibiting the most similarity to the measured parameters.
According to another aspect of the present invention a method of manufacturing a joint prosthesis for a patient""s bone is provided, comprising obtaining imaging data of the joint surface of the patient""s bone, modifying the imaged data of the joint surface of the patient""s bone to provide a more functional surface topography, fabricating a replicate of the modified imaged data to provide a functional joint prosthesis.
According to another aspect of the present invention a method of manufacturing a joint prosthesis for a patient""s bone is provided, comprising obtaining imaging data of the joint surface of the patient""s bone, comparing the imaged data of the joint surface of the patient""s bone with a database of mathematical descriptions of a plurality of articular joint surface archetypes, modifying the imaged data of the joint surface of the patient""s bone to provide a more functional surface topography while exhibiting the smallest deviation in overall dimensions from one of the plurality of articular joint surface archetypes, fabricating the joint prosthesis to resemble the articular joint surface archetype which exhibits the smallest deviation in overall dimensions from the modified imaged data.
According to another aspect of the present invention a method of manufacturing a joint prosthesis for a patient with a healthy contralateral joint is provided, comprising obtaining imaging data of the patient""s healthy contralateral joint surfaces, modifying the imaged data of the patient""s healthy contralateral joint surfaces to provide a more functional surface topography, fabricating a replicate of the modified imaged data to provide a functional joint prosthesis.
According to another aspect of the present invention a method of manufacturing a joint prosthesis for a patient with a healthy contralateral joint is provided, comprising obtaining imaging data of the patient""s healthy contralateral joint surfaces, comparing the imaged data of the patient""s healthy contralateral joint surfaces with a database of mathematical descriptions of a plurality of articular joint surface archetypes, modifying the imaged data of the patient""s healthy contralateral joint surfaces to provide a more functional surface topography while exhibiting the smallest deviation in overall dimensions from one of the plurality of articular joint surface archetypes, and fabricating the joint prosthesis to resemble the articular joint surface archetype which exhibits the smallest deviation in overall dimensions from the modified imaged data.
According to another aspect of the present invention an apparatus for manufacturing a joint prosthesis for a patient is provided, comprising memory means for storing a database of a plurality of joint surface archetypes acquired through measurement of a plurality of joint surfaces, said plurality of joint surface archetypes being cross-referenced by parameters including dimensions of bone associated with the joint surface, the weight of a person from whom the measurement is being taken, the sex of the person from whom the measurement is being taken, the race of the person from whom the measurement is being taken, and the height of the person from whom the measurement is being taken, input means for receiving a plurality of parameters exhibited by the patient, a microprocessor connected to said memory means for selecting one of said plurality of joint surface archetypes whose parameters most closely resemble a corresponding plurality of parameters exhibited by the patient, and a numerically-controlled fabrication means controlled by said microprocessor for fabricating the joint prosthesis to resemble the selected articular joint surface archetype.